The Boolean modifier is additive rather than removing mesh
First of all, I suggest you work with a lot less subdivisions, and use Smooth shade to hide the hard edges (Right Click -> Shade Smooth). I reduced your number of subdivisions to 1 and the Boolean worked fine, you'll also need to apply the Mirror modifier first.

Also, try changing the geometry of that concave section (the top part of the "cutter") as it's producing very fine geometry when subdividing, I assume that was the problem here.